Process for stabilizing chlorinated rubber



retenes aan is, rese attuati PRGESS FR STABMZHNG GMRJMTED RUBBER,

Karl Bromig, Frankfort-on-tlielwam, Germany, assigner to Deutsche Gold" und Silber-Scheide anstalt vormals Roessler, FranlrEort-cn-thcliiiain, Germany, a corporation or Germany No Drawing. dpplication March 22, i935, Serial No.. 125ML lin Germany April 3, 1934 l2 malins. ,(Cli 260ml) lThe object of my invention is a proces for stabilizing chlorinated rubber.

It is well known that products obtained by clilorinating rubber, for example in suitable solaccording to the prevailing conditions, they may for example be employed in solid, preferably finely powdered, former alternatively in the form of solutions in the same organic solvents as are 5 vents, contain the chlorine in part very closely used for dissolving the chlorinated rubber or in 5 c combined, in part however in an extremely labile other solvents of a similar kind.. Finally the condition, so' that on storing the product separaalkali salts may be employed in the form of tion of hydrogen chloride very soon takes place. their aqueous solutions, the solution of the chlo- Attempts have therefore already been made to rinated rubber in this case being vigorously lo stabilize the chlorinated product by treatment stirred or emulsified with the aqueous alkali salt with various alkaline-reacting media. The stasolution. y

bility numbers of the resulting, products, i. e. According to my invention it has been found the time intervals required by a 30% solution that the treatment of the finished chlorinated oi' the chlorinated rubber in xylene to tum red rubber solutions with small quantities of alkali congo paper, suspended 5 cms. above the surface salts may be carrim out at ordinary tempera- 15 of the liquid, blue on heating to 100 degrees centitures; in order to accelerate the action and to grade, however amounted to from only a few shorten the times of treatment, however, I may minutesy to a maximum of a few hours. Thus, also eiect the operation at elevated temperatures. for example, commercial, stabilized chlorinated According to my invention I have further found m rubber products of this. kind on carrying out that it is particularly advantageous to heat or the4 aforesaid test have proved to be stable for boil the solutions of the chlorinated rubber in from 2 to 10 hours and at the best for 20 hours, organic solvents, such as carbon tetrachloride or before the congo paper after the expirylof this 4the like before causing the alkali salts employed time showed a distinct blue owing to the separato act upon the same. As a result of this heat 2@ tion and liberation of the hydrogen chloride. treatment a part of the hydrogen chloride formed 25 The present invention is based on the discovery is already removed, so that relatively small quanthat considerably more stable products may be tities of stabilizing agents are sufficient to obtain obtained by treating the dissolved products, olothe desired degree of stabilization. tained by bchlorinating rubber in solvents, such The process of my invention is for example as carbon tetrachloride, chloroform, xylene or carried into effect by adding to an approximately 30 the like, after completion oi the chlorinating 10-l5% solution of chlorinated rubber in car- DIOCGSS, With Small quantities of 'alkali salts of bon tetrachloride 0.51.5% of sodium cyanide calorganic acids-which are themselves soluble in oulated on the chlorinated rubber in solution. the Solvents emplOyed and-WhOSe Salts are like- Another4 method of operating comprises treating WiSe t0 2 Certain degree Soluble in these Solvents. the chlorinated rubber solution, for example with 35 Suitable acids as aforesaid are, fOr eXample, sodium stearate. In this case such quantities of hYdrOCYaniC acid, fatty acids, SllCl1 aS PIODiOniG stearato are with advantage employed, that the acid, Steari afd and Dalmt@ acid, oleic acid 011 solution remains practically free from turbidity. the like. Thus, for example, salts, such as sodium In all cases the solutions are allowed to stand 4 cyanide, sodium stearato, sodium oleate or the for a certain time, for example for several hours, 4o like, may be emplOyed fOr the aforesaid pul'DOSe, at ordinary or elevated temperature. If the stal'ldividully 01' in dmxtul'e With One anOther. bilizing agents are employed in solid form they A 502D, Obtained by SapOnifyng COCOnllt Oil, haS are preferably suspended in a very finely pow-` fOl example proved t0 be serviceable and Dal'lilldered condition in the same solvent as is used for larly suitable. The Combined application of difdissolving the chlorinated rubber and the suspen- 4,5 ferent stabilizing agents according to the invension thoroughly mixed with the chlorinated rubtiOIl, OI' example by first adding alkali Cyanide ber solution. Mixing is inl this case preferably and then alkali Salts 0f the fatty aidS 01' 016i@ 'carried out at elevated temperature in order to ad, by adding a mixture of both agents or by accelerate the action. When the stabilizing rSt adding the alkali Salts 0f the fatty acids and agents are added in solid form to the chlorinated 5o the like and subsequently introducing the alkali rubber solution addition of about 2% calculated cyanide, has proved to be particularly advantaon the chlorinated rubber. is for example emgeous. ployed. l l The form in which the alkali salts are employed Products of extraordinary stability are obin the process of this invention may be selected tained by the process of my invention, for exitil ample products which have proved to be completely stable for 80, 100 and more hours.

The following examples serve to illustrate how the process of my invention may be carried into effect:

Example 1.-To 100 kgms. of chlorinated rubber dissolved in 750 kgms. of carbon tetrachloride, obtained by treating rubber with chlorine, there are added 0.8-1.2 kgms. of sodium cyanide, which hasbeen finely ground with carbon tetrachloride in a ball mill, and the mixture is allowed to stand for hours at 15-20 C. with stirring. The chlorinated rubber is then freed from solvent either in a vacuum roller drier or by precipitation with methanol-and dried. It is distinguished by high stability, light colour and practically unchanged viscosity.

Example 2.-40 kgms. of rubber are dissolved in chlorobenzene and converted by the action of chlorine into chlorinated rubber. 'Ihe solution, which at the conclusion of the chlorination contains l00 kgms. o f chlorinated rubber, is heated to boiling and maintained for 1 hour at boiling temperature. After cooling, 1.5 kgms. of .sodium stearato, which has been previously thoroughly ground with chlorobenzene, is allowed to run in and the mixture is allowed to stand for about 10- 12 hours with slight increase of temperature and stirring. 'I'he chlorinated rubber is recovered from the solution in known manner, for example as indicated in Example 1.

Example 3.-0.4 kgm. of a finely ground cyanide is added to a solution of 100 kgms. of chlorinated rubber in '750 kgms. of carbon tetrachloride, which after boiling has beenl cooled to about 45 C. After 4 hours the mixture is allowed to cooland 0.6 kgm. of sodium stearate is added. The reaction mixture is then allowed to stand with thorough stirring for a further 10 hours and is then worked up by the method indicated in Example 1.

It has already been proposed to produce chlorinated rubber by chlorinating solutions of rubber inthe presence of very large quantities of acid-fixing substances with simultaneous or subsequent heating to (iO-90 C. Alkali or alkaline earthscarbonates or blcarbonates, alkaline earths oxides or hydroxides, magnesium oiddes, sodium acetate and the like have been employed as acidfixing substances in quantities amounting to 200- 500% of the weight of the rubber.

In contradi'stinction to th'ese known processes very small quantities of stabilizing agents, amounting, for example, only to 0.5-2%, are employed according to my invention. These small quantities of stabilizing agents are, moreover, not added to the rubber solutions during-the prbcess of chlorination, but to the finished chlorinated rubber solutions after completion of the chlorinatlng process. In addition to effecting economies in stabilizing agents the process of this invention has the advantage that it yields satisfactory products even at ordinary temperature and is with `advantage carried out under gentle heating, for

example to 45 C. only when employing solid sta- 2. A process for stabilizing chlorinated rubber which consists in treating finished solutions of the chlorinated ,rubber in carbon tetrachloride with small quantities of alkali metal salts of or.

4which consists in treating nished solutions of `the chlorinated rubber in organic solvent with small quantities of alkali metal salts of hydrocyanic acid.

5. A process for stabilizing chlorinated rubber which consists in treating finished solutions of the .chlorinated rubber in organic solvent with not more lthan 2 percent of an alkali metal salt of organic acids selected from thegroup consisting of hydrocyanic acid and fatty acids of high molecular weight.

6. A process for stabilizing chlorinated rubber which consists in treating finished solutions of the chlorinated rubber in organic solvent with 0.5 to 1.5 percent of an alkali metal salt of organic acids selected from the group vconsisting of hydrocyanic acid and fatty acids of high molecular weight.

7. A process for stabilizing chlorinated rubber which consists in treating finished solutions of the chlorinated rubber in organic solvents with small quantities of alkali metal salts of organic l acids, selected from the group consisting of hydrocyanic acid and fatty acids of high molecular weight, effecting the treatment by adding the alkali metal salts dissolved in a solvent which is similar to the solvent used for dissolving the chlorinated rubber.

9. A process for stabilizing chlorinated rubber which consists in treating finished solutions of the chlorinated rubber in organic solvents with small quantities of alkali metal salts of organic acids, selected from the group consisting of hydrocyanic acid and fatty acids of high molecular weight, effecting the treatment by adding the alkali metal salt in a dry powdered form.

10. A process for stabilizing chlorinated rubber which -consists in treating finished solutions of the chlorinated rubber in organic solvents with small quantities of alkali metal salts oi' organic acids, selected from the group consisting of hydrocyanic acid and fatty acids of high molecular weight, effecting the treatment by adding the alkali metal salt in a dry powdered form raising the temperature of the chlorinated rubber solution during the treatment.

11. A process for stabilizing chlorinated rubber which consists in heating the finished solutions of chlorinated rubber in order to remove the maior portion of the dissolved hydrochloric acid,

cooling said solution and treating the cooled solution with small quantitiesof alkali metal salts of organic acids selected from the group consistfil ing of hydrocyanic acid and fatty acids of high molecular weight.

12. A process for stabilizing chlorinated rubber which consists in heating the finished solutions of chlorinated rubber in order to remove the major portion of the dissolved hydrochloric acid,

cooling said solution and treating the cooled solution with small quantities of a mixture of an alkali metal salt of hydrocyanic acid and an alkali metal salt of a fatty acid of high molecular weight.

KARL BROMIG. 

